Method of connecting post to joist
A bracket having a long leg and a base having three layers. A preferred bracket has support sides connecting the long leg and the base. Any bracket may be used to attach any portion of a structure which would tend to be separated from the remainder of the structure by a pulling or pushing force by laterally attaching the long leg to the main portion of the structure and laterally attaching the base to the portion of the structure which would tend to separate. A preferred use is a method of operatively connecting guard rail posts to deck joists or other structural elements.
This application is a continuation-in-part of Ser. No. 11/097,886 filed Apr. 4, 2005 which claims the benefit of the filing date of provisional application Ser. No. 60/600,719 filed Aug. 12, 2004.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT(Not Applicable)
REFERENCE TO SEQUENTIAL LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISC(Not applicable)
BACKGROUND OF THE INVENTION1) Field of the Invention
This invention is concerned with methods of attaching upright posts to structural elements. The posts are subject to forces which tend to pull or push them away from the other portions of the structure. This invention is also directed to particular brackets which aid in this method.
2) Description of the Related Art
Every deck builder knows full well the risks inherent in his or her occupation. Most injuries are related to builders getting cut, smashing body parts, getting nicked with saws, or stepping on nails. These are the daily risks that they try to guard against. However, the injuries that are most likely to take everything they have worked so hard for occur after they have packed up their tools, turned their work over to the homeowner, and are working on the next job. Years later, after they have moved on, timber has shrunk and settled, connections have loosened, and catastrophe occurs. A deck railing fails, giving way and spilling the occupants from the deck. There is no warning; there is no indication of risk, or of imminent danger. Wedding receptions and graduations turn from festive occasions into tragic news events. A few years will pass, depositions will be taken, and the contractor will lose everything.
Why? Because deck railings are hard pressed to handle the loads placed on them during the full service life. Railings are built with the carpenter not knowing what future demands will be placed on his work. Will a sports team enjoy a picnic on a deck that he or she has built and have eleven men lean or sit on the top rail? Will partygoers begin wrestling and fall into it?
Who decides what the appropriate load is and what is an acceptable margin of safety? These decisions are under the purview of the building code officials and their code writers. These officials quantify the load that a guardrail and handrail must absorb to obtain a reasonable level of safety. The Code for deck guardrails is found in the ICC International Residential Code (IRC) 2000 and 2003. IRC Tables, R301.4 and R301.5 define the minimum concentrated live load for guardrails and handrails as 200 lbs. The application of that load is described in Footnote “d”, Table R301.4 as “[a] single concentrated load applied in any direction at any point along the top”.
In acknowledgment that guardrails and railings in use may be subjected to conditions that are more demanding then those experienced in the testing process, the ICC employs an appropriate “safety factor”. Extreme conditions and variables such as improper installation, weathering, and excessive “in-use” loading require that a safety factor be applied to the load minimum. An industry standard safety factor of 2.5 has been derived from ICC code documents and testing requirements.
The inventor's testing indicated that the current guardrail designs do not meet IRC code requirements for load. Guardrails must be capable of resisting a load of 200 lbs, applied in any direction. When multiplied by the safety factor of 2.5 (200 lbs.×2.5=500 lbs) the guardrail assembly must resist a minimum of 500 lbs applied at any point along the top of the guardrail. Restated, each guardrail member must successfully withstand a load of 500 lbs, applied in any direction, to be IRC Building Code compliant.
Forensic examination of guardrail failures reveals a weak link in construction as being the deck guardrail post attachment methods and materials. When an occupant of the deck leans against the guardrail, he or she is using his or her weight to work against the post connections. This force, along with others, gradually weakens and ultimately causes the connection to fail. Because of this, much research has been done to understand and improve this connection.
In an effort to address this problem, the inventor spent several years examining the construction details of deck connections, defining the various modes of connection failure, and developing practical mechanisms to reinforce components in ways that resist the most prevalent modes of failure.
Historically, the guardrail post has been attached to the deck using one of two types of fasteners; lag bolts or carriage bolts. The process for installing each fastener type is similar; both requiring two fasteners to be installed near the bottom of the post and to be connected to the deck band board. However, each of these fasteners exhibits different modes of failure.
Lag bolts are installed by drilling through the post and into the band board and then screwing the lag into the band board. The threads of the lag are intended to grip the timber fibers of the band board. Ideally, the holes in the post and in the band board are made with different drill bits; one sized to allow the lag to pass through the post, and one sized to allow the threads to grip the band board. Although this connection has a rather large capacity to resist vertical loads, its ability to resist lateral and rotational loads applied to the post is limited. This limitation is due to the low capacity of lag bolts in tension due to pullout of the bolts through the timber band board.
Carriage bolts are installed in a similar fashion. Holes are drilled in the same location as with lag bolts, but the holes are sized to allow the carriage bolt to pass through both the post and the band board. The connection is achieved by the installation of a washer and retaining nut on the carriage bolt. When tightened, the assembly provides a through-bolted connection between the post and the band board of the deck. As with the lag bolt, this connection resists vertical loads well, but its ability to resist lateral and rotational loads applied to the post is limited. However, its limitation is related to the connection of the band board to the joists of the deck. While the connection of the post and band board generally remains intact, the load applied to the post causes the band board to be peeled off the ends of the deck joists. This is due to the method of connection typically used for band boards. Band boards are virtually always affixed to the deck with 16-penny nails installed in the end grain of the deck joists. This method possesses a surprisingly low resistance in tension, allowing pullout with relatively little force.
BRIEF SUMMARY OF THE INVENTIONTo counter the above shortcomings, the inventor developed methods and brackets that, among other things, greatly increase the lateral and rotational load-carrying capacity of the guardrail post-to-deck connection. These methods and brackets replace the lag bolt, carriage bolt or through-bolt connection with a much stronger connection that directs the force into the contiguous deck members, absorbing and distributing the energy of the load with reduced risk of injury to the deck occupants. The effect of this distribution is evidenced through bending of the timber post, twisting of the timber band board, and most importantly, deformation of the brackets. These distortions not only increase the ability of the railing system to accommodate lateral load, they also provide ample warning to the occupants of the deck that something is amiss.
The brackets of this invention have a long leg which fits against the sides of joists of the deck, a short leg, or base, which fits against the side of the object to be supported. The object to be supported may be a vertical deck post or a band board. The long leg and the short are connected to the joist, band board or deck post in a lateral (horizontal) direction. That is, the connector, be it a nail, a screw, or a bolt, lies in a plane parallel to the horizon when the connection is complete. The reason that the brackets give superior, unexpected results is that because of this direction of connection, there is no sudden breaking, but instead, a superior lateral and rotational load resisting ability and, ultimately, a gradual movement which preserves the integrity of the guardrail assembly and alerts the occupants in sufficient time to avoid the area and to have the weakened connections repaired. With the use of the special brackets and inventive methods of connection of the present invention, personal injury and the loss of life due to the present inferior deck connections can be avoided.
In further describing the method of the present invention, the long leg of a bracket is attached to the side of a joist of a deck or other weight-bearing, stationary portion of a structure, hereafter referred to a structural element. The attachment is made by bolts, nails or screws, hereafter referred to as mechanical connectors, passing laterally through the long leg of the bracket and into or through the weight-bearing stationary joist. The short leg of the bracket fits against the deck guard rail posts or deck band board which in turn is attached to a deck guard rail post or other portions of structures which are subjected to lateral and rotational forces which tend to pull or push them away from the stationary portions of the structure. The term “operatively connected” encompasses direct attachment between the deck guard rail post and the deck joist and a situation wherein the deck guard rail post is connected to the band board and the band board is connected to the deck joist. The attachment is made by at least one bolt passing laterally through the short leg of the bracket and into or through the portion of the structure which is subjected to forces which tend to pull or push them away from the stationary portion of the structure and at least one bolt passing laterally through the deck joist or other structural element. It is preferred to have more than one mechanical connector and it is preferred that the connectors be off of the center line of the bracket.
This invention discloses brackets 2 for securing second portions 4 of structures which are subject to pulling or pushing forces which would tend to separate the second portions from first (support) portions 6 of those structures. The description is concerned with operatively securing deck rail posts 4 to deck joists 6, but it should be realized that the invention is not so limited. Basically, any second portion 4 of a structure subject to a force which would tend to separate it from a first portion 6 of a structure by a pulling or pushing force may be secured to the first 6 portion of the structure using a bracket 2, preferably the preferred bracket 2 of the present invention. Examples of such other uses are attachments of rails to docks and headers to joists.
The bracket 2 of the preferred embodiment of this invention may be described as being an “L”-shaped bracket 2 having a long leg 8, a short leg (base) 10, and, preferably, two lateral support pieces 12, the base 10 being made up of three layers 14. The bracket 2 has at least one hole 16 in the long leg 8 for mechanical connectors such as nails, screws, and bolts and at least one hole 16 in the base 10 for mechanical connectors.
One method of preparing the preferred bracket 2 is set forth below. The method involves a first step of providing a sheet 18 of material, preferably metal, and most preferably steel, depending on the intended use. The metal, when used, may be a metal which has been treated by known methods so as to be resistant to chemical deterioration when exposed to atmospheric, chemical wood preservative, or oceanographic conditions. The thickness of the metal is suitable for the manufacture of a bracket 2 for holding a second portion 4 of a structure which is subject to a pulling or pushing force tending to separate it from a first portion 6 of the structure. A ⅛″ thickness is an example of such a thickness when the bracket 2 is to be used to strengthen house decks or boat docks. The material is so marked as to form an outline 20 of the shape of a long leg 8, with one lateral support piece 12 coming from each side thereof, and the long leg 8 and the two lateral support pieces 12 have extensions 22 of at least about ⅓ of the length of the long leg 8. The sheet 18 is trimmed so that it has the shape of a long leg 8 with one lateral support piece 12 coming from each side thereof and the long leg 8 and the two lateral support pieces 12 have extensions 22 of at least about ⅓ the length of the long leg 8. The shape of the lateral support piece 12 is not critical. Lateral support pieces for “L”-shaped brackets are known in the art, as see U.S. Pat. No. 5,467,570 granted to Leek Nov. 21, 1995 and U.S. Pat. No. 6,311,449 granted Morse et al Nov. 6, 2001. Thus, those skilled in the art are capable of formulating designs for lateral support pieces 12 which will offer adequate support. The sheet 18 is then cut, preferably by punching, so as to form a blank 24. The two lateral support pieces 12 along with their extensions 22 are then folded forward relative to the long leg 8. The extension 22 of the long leg 8 is then folded inwardly and the extensions 22 of the two lateral support pieces 12 are then folded forwardly by known methods of bending metal to form a three-layered 14 base 10. It is preferable that the extension 22 of the long leg 8 is on top. The sequence of folding the extension 22 is not critical. Appropriate holes 16 may be drilled or punched for mechanical connectors, such as bolts, nails, or screws.
In the manufacture of a bracket 2 having a long leg 8 and a three-layered 14 short leg or base 10, but no lateral support pieces, a metal blank 24 is prepared having a general “T” shape. The stem 26 of the “T” will be the long leg 8 and the cross 28 of the “T” will be the top layer 14 of the short leg or base 10 and two lateral extensions 22. The cross 28 of the “T” is folded forward to form a 90° angle with the stem 26. The cross 28 of the “T” is divided into three sections; the first 22 has the width of the stem 26, the second 30 and third 32 extend laterally from the first section and each has a width approximately the width of the stem 26. The second section 30 is folded by known means to lie adjacent to the first section 22 and the third section 32 is folded by known means to lie adjacent to the second section 30.
If the long leg 8 and its extension 22 are seen as forming an “L” when the blank 24 is folded, it is preferred that the second 30 and third 32 sections lie below the first section 22 of the “L”.
A similar bracket 2 may be prepared having a long leg 8 and a short leg 10, no supporting side, and having only two layers 14 in the short leg 10. In the manufacture of such a bracket 2, a metal blank 24 is prepared having a general “T” shape. The stem 26 of the “T” will be the long leg 8 and the cross 28 of the “T” will be the short leg 10 and two lateral extensions 30, 32. The cross 28 of the “T” is folded forward to form a 90° angle with the stem 26. The cross 28 of the “T” is divided into three sections; the first 22 has the width of the stem 26, the second 30 and third 32 extend laterally from the first section 22 and each has a width approximately ½ the width of the stem 26. The second 30 and third 32 sections are folded by known methods to lie adjacent to the first section 22.
In an alternative method of making a bracket 2 having a long leg 8 and a two-layered 14 short leg 10, but no lateral support pieces, an “L”-shaped blank 24 of metal having a long stem 26 and second 30 and third 32 shorter sections, each having the same width as the long stem 26, is used. The bottom portion 22 of the “L” shorter and the second 30 and third 32 sections are folded up to form a 90° angle with the long stem 26. The second shorter section 30 is folded so that it is underneath and adjacent to the first shorter section 22 and the third shorter section 32 is folded so that it is beneath the second shorter section 30.
Another alternative method of making a bracket 2 having a long leg 8 and a two-layered 14 short leg 10, but no lateral support pieces will be described. A single piece of metal blank 24 having a uniform length and width is provided, preferably by stamping. A first 900 fold is made at the desired length of the long leg 8 of the bracket 2, thus forming the long leg 8 of the bracket 2 and a second piece 34 in line with the long leg 8. The second piece 34 is folded in half by means known in the art to form a two-layered 14 short leg 10.
Other methods, such as welding one or more layers 14 to the short leg 10 of a bracket 2, may also be used to make the desired bracket 2.
As noted above, the bracket 2 is adapted to be used for holding a second portion 4 of a structure which is subject to a pulling or pushing force, and rotational force, tending to separate it from a first portion 6 of the structure. The bracket 2 may be used by laterally connecting the long side 8 to a first portion 6 of a structure, preferably by fitting mechanical connectors through pre-prepared holes 16 for this purpose. The base 10 of the bracket 2 is then laterally attached to a second portion 4 of the structure by fitting at least one mechanical connector through at least one hole 16 in the base 10 of the bracket 2 into a the second portion 4 of the structure. The mechanical connector may be a screw, a nail, or a through bolt, as the situation demands. More than one bracket 2 may be used in a given area. If two brackets 2 are to be used opposite the same portion 4, 6 of the structure, such as a joist 6, they may be place on opposite sides of the joist 6 and be connected by common through bolts.
Because of the lateral connection of the base 10 and the long side 8, the connection of the bracket 2 to the upstanding post 4 and the structural elements 6. The existence of these unexpected beneficial properties is demonstrated by the following tests.
A second portion of the present invention is a method of operatively connecting an upstanding post 4 to a structural element 6 that is oriented to resist moment so as to be compliant with the aforementioned IRC and building code performance and testing requirements. The method of this invention involves the placement of brackets 2 in such a way that lateral pressure against a guard rail at the top of the posts 4 does not result in the pulling out of the post 4, pulling off of the band board, or rapid breaking of the post 4 as is common when customary methods of attachment are used. Instead, the long side 8 of the bracket 2 is securely attached to a structural element 6 such as a deck joist 6 which holds firm. The base 10 or short leg 10 of the bracket 2 is operatively connected to the deck post 4. Lateral forces against the guardrail or guardrail post 4 in excess of code required limits causes the base 10 of the bracket 2 to yield, resulting in an outward movement of the deck post 4 and guard rail. This gives warning to the occupants to leave the area. Ultimately, continued lateral pressure would break the timber of the deck post 4 before the bracket 2 would give way and the pressure required for this is unexpectedly far greater than the pressure which would result in the destruction of a deck structure having the conventional placement of brackets.
During research performed in conjunction with the University of Maryland's Department of Civil Engineering, the inventor assessed test units replicating five different configurations that simulated current industry-standard methods for connecting timber deck guardrail rail posts 4 to deck structures 6. For each of the five configurations, three samples were tested to eliminate anomalies and for comparison of results.
The test units were constructed using pressure-treated SPF 4″×4″s attached to 2″×8″ band boards using hex-bolts, and the band boards in turn were connected to the deck joists using four 16-penny nails. Each unit was then tested on a fabricated steel load frame. A lateral load was applied to the top of each of the posts at a point 36″ above the deck surface to simulate the load typically experienced by a deck railing post.
These tests do not take into account the effects of weathering. Deck components and their connections deteriorate over time. The load capacity of screws, nails, hardware, and wood products diminish with use and age. These test units were constructed with new lumber and fasteners. It is most probable that the load capacity of these, or any connections, would diminish with the effects of time and weathering.
Test Load Frame:To compare the effectiveness of the test units, a fabricated steel load frame was constructed. The purpose of the load frame was twofold: to support the test units to simulate real life conditions, and to provide a mechanism with which load could be applied and quantified as the test units were stressed to failure.
The load frame used for the following tests was fabricated from 2″ angle steel, welded into a 4′×5′ rectangular test bed. By welding angle steel legs to the frame, slots were created to confine the deck joists. Holes were drilled through the steel slots where ½″ pins would be inserted to lock the test units into the load frame. Steel risers were welded to the load frame to hold the test units above the frame. This allowed the guardrail post and the deck band board that was being tested to react and move independently without contacting or binding on the load frame itself.
Load was applied by means of a cable puller with one end hooked to a calibrated and certified dynamometer and the other to a steel ring, affixed to the 4″×4″ timber post being tested. The ring was positioned at a height of 36″ above the deck surface, as required by IRC Building Code.
This series of tests assumed that, in railing failure, the deck joists remain in place. The tests simulated this condition by affixing the deck joist to the steel frame such that only the joists were anchored. For each test, lateral force was applied to the top of the 4″×4″ until failure occurred or until the force exceeded that which the equipment could safely withstand (1,350 lbs. to 1,500 lbs.). For this series of tests, guardrail post failure was defined as a condition where deck occupants would no longer be safely corralled by the guardrail. As long as the post remained in a semi-vertical position and retained structural integrity, the test continued.
The tests were stopped by catastrophic events, such as post failure or excessive movement of the post. Each of the five configurations was tested with three separate samples (A, B, and C) to allow results to be averaged.
Test Unit Configurations Test 1 Control Test Unit:For this test, the 4″×4″ post was mounted outside of the band board, between the connection points of the two deck joists. The band board was attached to the ends of the deck joists using sixteen-penny nails, three on each joist, installed with a pneumatic nail gun. No brackets were used in this test.
Results:The nails pulled out of the deck joists, dislodging the band board and the attached post at a load of 150 lbs—far below the IRC Code requirement of 500 lbs. Since the band board was attached to each of the three deck joists, each connection provided approximately 50 lbs resistance to pullout.
Bracket Test Units:The configuration with brackets 2 for Test 1 is shown in
The post was mounted on the outside of the deck band board 4 equidistant from the two deck joists 6. The 2″×8″ deck joists 6 were set at 16″ O.C. The brackets 2 of this invention were located with the center of their bases 10 located against the inside of the band board 4 and their long sides 8 flush against a deck joist 6. The brackets 2 were attached to the deck joists 6 by two, 2½″ long, ½″ hex-bolts and nuts, utilizing ½″ flat washers on each side. A 2½″ long, ½″ hex-bolt, with flat washers and retaining nut secured the brackets 2 to the band board 4. All nuts were tightened to approximately 30 lbs/ft of torque. In attaching the bracket 2 to the band board 4 or upstanding post in this and the following tests, the bolt connector was positioned horizontally. Also, in attaching the bracket 2 to the deck joist 6 in this and the following tests, the bolt connector was positioned horizontally. Thus, the bracket 2 is referred to in this specification as a lateral anchor 2.
Results: 1A: Timber failure of the 4″×4″ post at 700 lbs. 1B: Timber failure of the band board at 525 lbs. 1C: Timber failure of the band board at 600 lbs. Test 2 Control Unit:For this test, the 4″×4″ upstanding post was mounted inside of the band board, between the connection points of the two deck joists. The band board was attached to the ends of the deck joists using sixteen-penny nails, three on each joist, installed with a pneumatic nail gun. No brackets were used in this test.
Results:The nails pulled out of the deck joists, dislodging the band board and the attached 4″×4″ post at a load of 100 lbs. Since the band board was attached to each of the three deck joists, each connection provided approximately 33 lbs resistance to pullout.
Bracket Test Units:The configuration for test two is shown in
The 4″×4″ post was mounted on the inside of the deck band board 4, between the two deck joists 6. The 2″×8″ deck joists 6 were set at 16″O.C. The brackets 2 of this invention were located with their bases 10 against the inside of the band board 4 and their long sides 8 flush against a deck joist 6. The brackets 2 were attached to the deck joists 6 by two, 2½″ long, ½″ hex-bolts and nuts, utilizing ½″ flat washers on each side. A 2½″ long, ½″ hex-bolt, with flat washers and retaining nut secured the brackets 2 to the band board 4. All nuts were tightened to approximately 30 lbs/ft of torque.
Results: 2A: Timber failure of the 4″×4″ post at 525 lbs 2B: Timber failure of the band board at 525 lbs 2C: Timber failure of the band board at 500 lbs Test 3 Control Unit:For this test, the 4″×4″ upstanding post was mounted outside of the band board, located adjacent to the point of connection of a single deck joist. The band board was attached to the ends of the deck joists using sixteen-penny nails, three on each joist, installed with a pneumatic nail gun. No brackets were used in this test.
Results:The nails pulled out of the deck joists, dislodging the band board and the attached 4″×4″ post at a load of 75 lbs. Since the band board was attached to each of the three deck joists, each connection provided approximately 25 lbs resistance to pullout.
Bracket Test Units:The configuration for test three is shown in
For this test, the 4″×4″ upstanding post was mounted outside of the band board 4, located adjacent to the point of connection of a single deck joist 6. One bracket 2 according to this invention was utilized to anchor the 4″×4″ through the band board 4 to the deck joist 6. Thus, the upstanding post was operatively connected to the deck joist 6. The bracket 2 was located with its base 10 against the inside of the band board 4 and the long side 8 flush against a deck joist 6. The bracket 2 was attached to the deck joist 6 by two 2½″ long, ½″ hex-bolts and nuts, utilizing ½″ flat washers on each side. All nuts were tightened to approximately 30 lbs/ft of torque.
Results: 3A: Timber failure of the 4″×4″ post at 600 lbs. 3B: NO FAILURE Test stopped at 1,500 lbs to avoid damage to testing equipment. 3C: NO FAILURE Test stopped at 1,350 lbs to avoid damage to testing equipment. Test 4 Control Unit:For this test, the 4′×4″ was mounted inside of the band board, located adjacent and contiguous to a single deck joist. The band board was attached to the ends of the deck joists using sixteen-penny nails, three on each joist, installed with a pneumatic nail gun. No brackets were used in this test.
Results:The nails pulled out of the deck joists, dislodging the band board and the attached 4″×4″ post at a load of 65 lbs. Since the band board was attached to each of the three deck joists, each connection provided approximately 22 lbs resistance to pullout.
Bracket Test Units:The configuration for test four is shown in
For this test, the 4″×4″ was mounted inside of the band board 4, located adjacent and contiguous to a single deck joist. The 2″×8″ deck joists 6 were set at 16″ O.C. One bracket 2 was utilized to anchor the 4″×4″ and band board 4 to the deck joist 6. The bracket 2 was located with its base 10 against the inside of the 4″×4″ and the long side 8 flush against a deck joist 6. The bracket 2 was attached to the deck joist by two, 2½″ long, 2″ hex-bolts and nuts, utilizing ½″ flat washers on each side. The base 10 of the bracket 2 slipped over the end of the upper 2″×8″ ½″ hex-bolt that secured the post. All nuts were tightened to approximately 30 lbs/ft of torque.
Results: 4A: NO FAILURE. Test stopped at 1,350 lbs to avoid damage to testing equipment.4B: Timber failure of the 4″×4″ post at 900 lbs. The dynamometer jumped to 1,400 lbs indicated when 4″×4″ broke.
4C: NO FAILURE. Timber failure of the 4″×4″ post at 525 lbs. Test 5 Control Unit:For this test, the 4″×4″ was mounted on the inside of the terminal deck joist to replicate the mounting of a rail post for protection along the side of the deck. The band board and the ledger boards were attached to the ends of the deck joists using both sixteen-penny nails, three on each joist, installed with a pneumatic nail gun, and with 3½″ deck screws, three on each deck joist. 5/4″ board deck tread was screwed to the deck joists, but it did not contact the terminal joist on which the 4″×4″ was mounted. No brackets were used in this test.
Results:The nails and the screws pulled through the ends of the terminal deck joist, splintering the timber at each end, dislodging the band board and the attached 4″×4″ post at a load of 220 lbs.
Bracket Test Units:The configuration for test five is shown in
For this test, the 4″×4″ was mounted on the inside of the terminal deck joist 6 to replicate the mounting of a rail post for protection along the side of the deck. One bracket 2 according to this invention was bolted to the 4″×4″ and to the 2″×8″ block and a second bracket 2 was bolted to the deck joist 6 and the 2″×8″ block. As in the other tests, the 5/4″ board deck tread was screwed to the deck joists 6 that were not in contact with the 4″×4″ post. The 2″×8″ deck joists 6 were set at 16″ O.C. One bracket 2 according to this invention was located with its base 10 against the inside of the 4″×4″ and the long side 8 flush against the 2″×8″ block. The second bracket 2 was located with its base 10 against the deck joist 6 and the long side 8 flush against the 2″×8″ block. The brackets 2 were attached to the 2″×8″ block by two, 2½″ long, ½″ hex-bolts and nuts, utilizing ½″ flat washers on each side. A 2½″ long, ½″ hex-bolt, with flat washers and retaining nut secured the brackets 2 to the deck joist 6 and the 4″×4″. All nuts were tightened to approximately 30 lbs/ft of torque.
Results: 5A: NO FAILURE. Test stopped at 1,350 lbs to avoid damage to testing equipment. 5B: NO FAILURE. Test stopped at 1,500 lbs to avoid damage to testing equipment. 5C: NO FAILURE. Test stopped at 1,350 lbs to avoid damage to testing equipment.The bracket 2 used in the testing was the preferred bracket 2, that is, an “L-shaped bracket 2 having a three-layered 14 base 10 and side support pieces 12 connecting the base 10 and the long leg 8. This method of connection and bracket 2 strengthened the connection of the band board to the joists and allowed the lateral force to be redistributed to other structural elements. With every test that was run, the primary failure was ductile, not timber failure. That is, the rail post (4″×4″) was allowed to shift slightly, transfer load to the deck structure and then remain substantially intact. This introduces a controlled predictable mode of failure and moves catastrophic failure to a secondary failure position. The method of connection and brackets 2 exhibited excellent ductility allowing for a reasonable warning for the occupants of the deck that the restraint system, (deck guardrail), was in danger of being overloaded and pushed to failure. That same ductility also allowed for a realignment of the timber members of the deck to more effectively absorb energy.
It should be noted that there was inconsistency in the load capacity between the 4″×4″s used in the testing. Each timber was examined carefully, picked for those with the fewest knots, cracks, or checking. Yet the difference in their load strength was surprising. The 4″×4″ post from test 2A experienced total failure at 525 lbs., where a similar 4″×4″, bought from the same lot, the same day, the same store, withstood 1325 lbs. and did not fail (The test was stopped to avoid damage to testing equipment and testers).
Meeting building code requirements for load capacity of a guardrail post is challenging because of the geometry involved and the building materials typically used on residential decks. The leverage created by the 36″ height of the post (above the tread) requires a substantial anchoring method to meet the 500 lbs ICC load testing requirement. The test units replicating current building techniques did not come close to providing the required load capacity. By simply using the proposed methods and attaching the bracket laterally to the joist and the upstanding post, the code conforming load of 500 lbs was met and exceeded in each and every configuration tested.
These tests were performed using new timber, new connectors, and new fasteners. As with all things, exposure to the elements and time likely will weaken the components and reduce their load capacities. This is left for future research and testing.
The table below summarizes the test results. The reader should notice the drastically improved lateral load capacity with the novel methods used and brackets 2 installed. The load capacities shown in the column titled “Load capacity with DECKLOK” reflect the average of the three test units in each configuration. Please note that, in each test of every configuration, the minimum load required by the IRC was met and exceeded.
SUMMARY TEST RESULTS
Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.
Claims
1. An “L”-shaped bracket having a long leg and a base wherein the base is made up of exactly three layers.
2. The bracket of claim 1, wherein supporting sides connect the base and the long leg.
3. The bracket of claim 1, wherein each of the long leg and the base has at least one hole therethrough for the passage of attachment devices.
4. The bracket of claim 1, wherein the bracket is metal and the metal has been treated to resist chemical deterioration.
5. A method of attaching an upstanding post to a structural element so that the upstanding post is capable of resisting moment and so as to be compliant with the building code testing protocol of 500 pounds capacity at a guard height of 36 inches by virtue of the fact that a bracket transmits lateral and rotational loads from the post to the structural element, which method comprises the steps of operatively connecting the upstanding post to one or more lateral anchors using mechanical connectors and attaching the one or more lateral anchors to the structural element using horizontally positioned mechanical connectors,
6. The method of claim 5, wherein the lateral anchor is an “L”-shaped bracket.
7. The method of claim 6, wherein the “L”-shaped bracket has a base which is made up of a plurality of layers.
8. The method of claim 7 wherein the bracket has a base which is made up of exactly three layers.
9. The method of claim 6, wherein the bracket has supporting pieces connecting the long leg and the base.
10. The method of claim 6, wherein the long leg of the “L”-shaped bracket is laterally attached to the structural element and the base of the “L”-shaped bracket is laterally attached to the upstanding post.
11. The method of claim 9, wherein each of the long leg and the base of the bracket has at least one hole therethrough for the passage of connector devices.
12. The method of claim 6, wherein the upstanding post is an upstanding deck post and the structural element is a deck joist.
13. The method of claim 6, wherein the mechanical connectors are bolts, nails, or screws.
Type: Application
Filed: Oct 26, 2007
Publication Date: May 22, 2008
Inventor: Michael G. Morse (Brookeville, MD)
Application Number: 11/977,709
International Classification: E04B 1/38 (20060101);
